To determine the effect of age on exercise left ventricular volumes, independent of physical fitness level (F), we gated cardiac blood pool scans during graded maximal upright cycle exercise in 95 healthy men ages 23-86 years were analyzed. In the overall group left ventricular end diastolic volume index (EDVI) and end systolic volume index (ESVI) increased with age (r=0.37, p< .01 and r=0.46, p<.001 respectively) while left ventricular ejection fraction (LVEF) declined with age, r= -0.46, p<.001 and stroke volume index (SVI) was unrelated to age. In a subset of 49 men of homogenous fitness (maximal workload 125-150 watts), EDVI and ESVI increased and LVEF decreased with age as in the overall sample bur SVI now increased with age (r = 0.39, p < .01) due to an accentuated increased in EDVI (r = 0.51, p < .001). We tested whether acute beta-adrenergic blockade with propranolol altered the hemodynamic response to exercise seen with normative aging. In 85 healthy BLSA men not give propranolol, left ventricular EDVI increased with age (r=-0.41, p< .001), LVEF, heart rate (HR) and cardiac index (CI) declined with age (r=-0.45, p<.001, r=-0.78, p<.001, and r=-0.33, p<.01) respectively and SVI was not age related. In 25 men ages 28-72 years given intravenous propranolol, EDVI declined with age (r=-0.20) causing an age-associated decline in SVI (r=0.48, p<0.05) not present in the unblocked men. The decline in heart with age in propranolol-treated men was blunted (0.46 beats/min/yr) compared to controls (1.09 beats/min/yr). The primary reason for the slope shifts in the age regressions in the presence of propranolol was a large increase in EDVI and SVI and a large decrease in HR in younger men. Thus, while the age-associated decline in maximal EF is unaffected, acute beta blockade reverses the age-associated ventricular dilatation during upright cycle exercise and blunts the decline in maximal HR. The net effect is an accentuated decline of maximal CI with age.